The Inferior Vena Cava (IVC) is the largest vein in the body returning the majority of the venous return to the heart. The mean diameter has been reported to be 20 m.m. with a range from 13 to 30 m.m. with a standard deviation of 3 m.m.--see Prince, M R et al. in Radiology 1983, December: 149 (3) 687-9.
The (1) Retrohepatic vena cava, (2) Vena cava between the Right atrium and the Right renal vein, (3) The Supra hepatic vena cava, have been measured by Rodrigues A. J. Junior et al., Gegerbaurs Morphol. Jahrb 1987, 133 (4); 665-72. and reported respectively to be: (1) 78.34 m.m., (2) 135. 16 m.m. and (3) 19.34 m.m.
Additionally Dr. Hee Lee at the District of Columbia General Hospital (Table I) has measured the IVC in the adult men and women utilizing the Computerized Tomogram and found the average length of the Vena Cava from the Right atrium to the left renal vein to be 134.2 m.m. and 124.4 m.m. in males and females respectively; and 132.2 m.m. and 123.6 m.m. in males and females respectively from the Right atrium and the right renal vein.
The IVC is often injured in penetrating trauma to the abdomen. Mortality is especially high-in the order of 90% when the retro hepatic Vena Cava is involved primarily for the following reasons:
1. Massive hemorrhage often results from disruption of the vena cava or attempts to expose the injured vessel in this difficult to access area lying posterior to the liver. 2. Acute interruption of the IVC by clamping the IVC above and below the liver may produce a nonperfused retrohepatic segment but severely reduces the venous return to the heart with the consequence of inadequate cardiac output and venous congestion and metabolic disturbances in the abdominal viscera and the lower extremities that often result in the death of the patient.
In an attempt to avert the disastrous consequences of hemorrhage and the acute interruption of venous return consequent to IVC interruption described above, surgeons have historically created an internal vena cava shunt mainly by one of two techniques: In the first technique, a chest tube has been placed into the IVC through the right heart after which the IVC would be encircled above and below the liver and tied down to the internal chest tube thereby creating an avascular segment in the area of injury and an internal shunt allowing blood to return to the heart through an opening in the chest tube customized to lie within the right atrium. This technique is often unsuccessful as encircling the vena cava below the liver can be difficult and can also result in inadvertent injury to other vessels with consequent bleeding from additional sites.
In a second technique, surgeons have employed an endotracheal tube to insert into the IVC similarly through the right atrium, followed by ligation of the intrapericardial IVC around the endotracheal tube after which the balloon of the endotracheal tube would be blown up in the suprarenal IVC forcing the blood to shunt into the lower opening of the tube and exit through an opening customized to lie in the atrial portion of the tube. In this manner the cerclage of the vena cava below the liver with its inherent potential problems would be avoided.
In the two techniques above, one has to make a judgment each time how far to insert the tube, where to customize the atrial opening and where to place the inferior ligature or inflate the balloon with respect to the renal veins and where to apply the proximal ligature with respect to the proximal customized opening in the tube to permit venous return to the heart.
Given the above anatomic, physiologic and technical considerations, an improved shunt for the retrohepatic IVC is hereby proposed that would:
1.) Be based on the known anatomic dimensions of the adult suprarenal IVC.
2.) Eliminate the need for customization of devices not originally intended for the shunting of blood or for use in this location.
3.) Provide a method for the easy and accurate identification of the site within the pericardium for the fixation of the device within the venous system which would also occlude the IVC above the retrohepatic IVC thereby preventing reflux of blood from the heart; and also obligate the caudal IVC occlusion balloon to position below the retrohepatic IVC segment; which when inflated would provide for bypass of the retrohepatic IVC and an internal shunt of blood from the renal veins and the suprarenal IVC to return to the heart.
This dedicated IVC shunt and stent, hereafter referred to as the Anderson Shunt, is depicted in FIGS. 1, 2, 3, 4, 1C and 2C, and is described in the following specifications and descriptions: